To provide a strong threaded opening in a plastic body or a cast body of soft metal, such as aluminum, it is common practice to provide a helical wire insert to define the threads in the opening. Thus, normal practice after a body has been molded or cast involves drilling a hole in the body at the desired location of the threaded opening, tapping the hole, inserting the helical wire configuration and then removing tangs or bent end portions to provide the final threaded insert construction. The helical wire itself may be made of stainless steel to provide strength and minimization of corrosion and the end product results in a strong threaded opening in the plastic or soft metal body which serves to receive threaded fasteners for various purposes in assemblying structures utilizing such bodies.
The foregoing process of providing the threaded openings is relatively expensive and time-consuming. Further, there is often not provided a thorough locking of the helical insert itself within the tapped opening against rotational as well as axial movement.
In some instances wherein concrete type material is used, a threaded insert opening has been provided by molding or casting the concrete about a helical wire configuration held in position with the actual fastener used. The problem with this particular process is the fact that metal and plastic materials tend to shrink when they solidify and thus the final pitch of the threaded opening is different from the designed pitch of the helical insert.